RTDs are well known for measuring temperature based on their coefficients of resistivity. RTDs operate on the principle of changes in electrical resistance of pure metals and are characterized by a linear positive change in resistance with temperature. When heated, the resistance of the metal increases; when cooled, the resistance decreases. Passing current through an RTD generates a voltage across the RTD. By measuring this voltage, you determine its resistance, and thus its temperature. Typical elements used for RTDs include nickel (Ni) and copper (Cu), but platinum (Pt) is by far the most common because of its wide temperature range, accuracy, and stability. RTDs are popular because of their excellent stability, and exhibit the most linear signal with respect to temperature of any electronic temperature sensor.
RTDs are typically constructed by one of two different manufacturing configurations. Wire-wound RTDs are constructed by winding a thin wire into a coil. A more common configuration is the thin-film element, which consists of a very thin layer of metal laid out on a plastic or ceramic substrate. Thin-film elements are cheaper and more widely available because they can achieve higher nominal resistances with less platinum. To protect the RTD, a metal sheath encloses the RTD element and the lead wires connected to it. Such metal sheaths as are currently known in the art, however, when submerged in a fluid such as water for up to 24 hours, for example, are not capable providing an adequate seal around the element and wires without a leak.
Thus there is a need for an RTD connector seal to couple and seal an RTD element to an RTD cable so that the RTD connector seal is capable of remaining submerged in a medium for a period of time while obtaining temperature data. There is also a need for a method of connecting an RTD element to an RTD cable in an RTD junction box so that the RTD element, cable, and junction box are capable of remaining submerged in a medium for a period of time while obtaining temperature data.